In-plane transport chirality in the ferromagnetic Weyl semimetal MnSb₂Te₄

Intrinsic van der Waals (vdW) magnets in the MnX₂Te₄ materials class (X= Bi or Sb) provide an important platform for exploring unconventional electrodynamics arising from the interplay between the nontrivial band topology and magnetism. While the antiferromagnetic (AFM) MnBi₂Te₄ (MBT) is a known topological insulator, MnSb₂Te₄ (MST) is less understood for the Sb/Mn interchange (antisite) defects can turn an AFM MST into a complex ferromagnet (FM). Here, using angle (φ) resolved in-plane magnetotransport measurements in conjunction with theoretical modeling we show that an FM MST is a Type I Weyl semimetal (WSM) with oppositely tilted Weyl cones displaying a giant field-antisymmetric planar Hall effect (PHE), the hallmark of chiral anomaly in a WSM. The in-plane anisotropic magnetoconductance follows a cos²φ behavior and the PHE varies as sinφ, as anticipated by theory which allows us to extract the corresponding inter- to intra-node scattering ratios characteristic of tilted Weyl nodes. We show that the in-plane transport is φ-chiral, namely, there is a large chirality metric χ^±φ owing to the difference between PHE values at ±φ. We also detect an unusual φ-chiral in-plane hysteresis loop, arising from the out-of-plane Berry curvature, which is tunable by hydrogenation [1]. The hydrogen-induced Weyl node modification and chirality amplification in FM MST, and the corresponding correlation with magnetic anisotropy changes rationalized by the ab initio calculations will be discussed.